Full Depth Reclamation (FDR) is a pavement rehabilitation technique in which the full flexible pavement section and a predetermined portion of the underlying materials are uniformly crushed, pulverized or blended, resulting in a stabilized base course; further stabilization may be obtained through the use of available additives. (ARRA)
All pavement structures, with the passage of time and traffic, wear out. In the past it has been convenient to overlay these roadways with additional layers of materials, thereby extending their service lives. Eventually, however, due to many factors, these roadways deteriorate to a point that conventional maintenance and/or repair and overlay practices become expensive and do not perform well due to the condition of the underlying structure. It is at this stage in a pavement’s lifecycle that costly roadway reconstruction is typically specified. However, due to the evolution of high horsepower road reclaimers with state of the art computerized additive systems, FDR is one of the fastest-growing rehabilitation techniques being specified by pavement engineers around the world. The process has been proven on a wide range of flexible pavement structures to produce quality results at substantially lower costs and considerably shorter construction periods than conventional reconstruction practices.
Full Depth Reclamation (FDR) is distinguished from other rehabilitation techniques like Cold Planing (CP), Cold In-Place Recycling (CIR) or Hot In-Place Recycling (HIR), by the fact that the rotor or cutting head always penetrates completely through the asphalt section into the underlying base layers, thereby erasing deep pavement crack patterns and eliminating the potential of reflective cracking. With today’s innovative equipment and vast range of stabilizing additives, FDR can be utilized to depths exceeding 12”, although it is typically performed at 6”- 9”. The pulverized layers and additive(s) become a homogeneous well graded (2”/50mm minus) material with improved structural characteristics.
Full Depth Reclamation (FDR) provides the ideal opportunity to add stabilizing additives to the new base, either solely or in a variety of combinations, to further enhance the characteristics of the reclaimed material. For example, bituminous stabilizing agents, in the form of asphalt emulsion or foamed asphalt, may be added to achieve a flexible bound material with high fatigue resistance. For added compressive strength, Portland cement or fly ash is sometimes blended with new base. To reduce plasticity and improve load-bearing characteristics, the addition of lime may be specified. If necessary, additional granular material can also be added for improving gradation and/or lessening the asphaltic binder content, thereby increasing the structural characteristics of the base.
By Thomas Fairfax